Variable electrostatic condenser



Dec. 13, 1927. 1,652,158

W. AULL, JR l VARIABLE ELETROSTATI C CONDENSER Y- Filed NOV. 29. 1922 NVENTOR M750/7 ull/ l/r BY M 7* A TTORNE Y Patented Dec. i3, i927.-

. STATES 'WILSON A'ULL, JB., 0F NEW YORK, Il'. Y., Aslm', BY MESNE ASSIGNMENTS, T0

D'UIBILIER CONDENSER CORPORATION, @E NEW YEK, N. Y.

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LE ELEGTIR'OSTATIC GGNDENSER- Application med November 29, 1922. Serial No. 603,924

This invention relates to variable electrostatic condensers, its principal object bein the revision of a variable condenser o sma volume per unit capacity as compared with variable condensers which have heretofore been in commonuse, such as the wellknown variable air condenser.

Since the capacity of a condenser for any given dielectric is inversely pro ortional to the distance between plates, it ollows that the capacity per unit volume of variable air condensers is extremely low on account of the necessity of providing comparatively large separation between the plates'.

In a co endin ap lication of William Dubilier erial o. 5 6,235, filed July 20, 1922, there is` describedl a variable condenser yin which the separation between plates is extremely small, the volume of the structure ao per unit capacity being correspondingly reduced. In the Dubilier condenser referred to, the plates are separated by thin sheets of mica, and the movable plates are in frictional engagement with the mica. The mica as dielectric has a constant ran in from 4 to 8 times that of air, a factor w ic combined with the small separation obtainable, results in increasing the capacity per unit area of the plates to such an extent that the size of 3o the structure for a given capacity is a relatively small raction of that of an equivalent variable air condenser.

The present invention embodies the advantages of the Dubilier condenser referred as to, but is an improvement thereon in that it provides a variable condenser in which friction between the adjustable plate or plates` and the dielectric is substantially elimi-.

nated.

Instead of rubbing the variable plate over the surface of the mica separator, as in the Dubilier condenser, the capacity variations are made by flexing the variable late or what may be conveniently termed picking up land layin down operations of the variable plate. hese terms will be clearly defined hereinafter.

In one of the preferred.embodiments of the invention, the fixed plate is in the form 5o of an annulus, and a thm layer of mica or other suitable insulatin material is secured to its inner surface. The variable plate has the form of a spiral similar to that of a clock spring, and its inner end is attached to a ro- The invention may take a number` of ali ternative forms, two of which are illustrated in the drawing and described in detail hereinafter.

Referring now to the accompanying drawig. 1 is a cross-sectional view taken along the-line 1--1 of Fig. 3 of a variable condenser constructed in accordance ywith this invention;

lFig. 2 is the same as Fig. 1, except that it illustrates a dierent operative position of the variable plate or spiral;

Fig. 3 is a ongitudinal section of the condenser shown in Figs. 1 and 2;

Fig. 4 is a cross-sectional view of an alternative form of condenser in accordance with the invention;

Fig. 5 is a cross sectional view of another alternative form of condenser in accordance with the intention; and

Fi 6 is a cross-sectional view of still anot er alternative form of condenser constituting a modification of the form shown in Fig. 4.

The condenser structure shown in Figs. 1, 2 and comprises a fixed plate having the form of a cylindrical casing 1. The inside of this casing is lined with a thin layer of mica or other suitable insulatin material 2. A variable plate 3, having e form of a spiral, is insulatively secured at its outer end to the casing 1 by means of a binding ost 4, to which it is electrically connecte The inner end of the variable plate 3 is connected to'an arm 5', which is integral with the rotatable` shaft 5. last-mentioned shaft is journaled in the bushin 6 and 7, which are preferably of insulatm material such, for instance,-as hard rub er. One end of shaft 5 is provided with. a lmob 8 of insulating material, to which is secured a lmetal disc- 9, the latter lbein kept out of contact'with shaft 5. A

meta block 10 is secured, in any convenient manner, to the casing 1, and is provi-ded with a s101510 of suiiicient width to allow the The.`

'against the tension of the variable plate 3,

which, in effect, is equivalent to a clock spring. A comparative examination of Figs. 1 and 2 will show, almost at a glance, the operation of this device. In Fig. 2 the shaft 5' has been rotated 180 from the position in which itis shown in Fig. 1, and, as will be seen, the exterior surface of the variable plate 3 bears against the mica lining 2 over an arc of approximately 200. It will be seen that the rotation of shaft 5 in a counterclockwise direction as viewed in Figs. 1 and 2, has the effect of what is appropriately termed laying down the variable plate on the mica 2, as distinguished from any fric tional action. This laying downI operation, it will also be seen, is progressive in its nature, that is to say, it begins at or near the point where the variable plate 1s at tached to the casing 1, and moves around in a clockwise direction. Rotation of shaft 5 in a clockwise direction, as viewed in Figs. 1 and 2, has the effect of what is appropriately termed picking upthe fixed plate. If the shaft 5 in Fig. 2 were turned in a clockwise direction, as there viewed, the picking up action would start at about the oint a and progress in a counter-clockwise irection toward the point at which the outer end of the fixed plate is attached. This icking u and laying down operation shoul be care ully distinguished from any operation in which the variable plate is moved bodily toward or away from a fixed plate. Electrical connections may be made to the variable plate 3 by means of the binding post 4, and to the fixed plate or casing 1 y means of the binding post 12.

In the alternative structure of Fig. 4, the casing 13 corresponds to casing 1 of Figs. 1, 2 and 3, and is likewise lined on its inner surface with a layer 14 of mica or other suitable insulating material which corresponds to the lining 2 in Figs. 1, 2 and 3. The curved variable plate 15 corresponds to the variable late 3 of Figs. 1, 2 and 3, and is so shaped) that when the arm 16 is rotated in a counter-clockwise direction the knob 17, which is attached thereto, will press against the lining 14, thereby progressively laying down the variable plate on the lining 14. The variable plate 15 is insulatively secured to the casing 13 by means of binding post 18, as is clearly shown.

In the alternative structure of-Fig. 5, the fixed plate is in the form of an annulus 19, to the exteriorsurface of which is attached an arcuate/,layer of mica or other suitable insulating material 20. The curved variable plate 21 is insulatively secured to fixed plate 19 by means of a rivet 22 or any other convenient attaching device. An arm 23 is attached to and is rotatable with shaft 24, and to the end portion of this arm is secured a roller 25, which bears against'the exterior surface of the variable curved plate 21. It will be readily seen that a rotation of shaft 24, together with arm 23, in a counter-clockwise direction, as viewed in Fig. 5, will result in forcing against or in other words laying down the variable plate 21 on the mica layer 20. The mechanism of this device is enclosed within a casing 26, which perfoims no function other than that of mechanical protection for the Operating parts of the mechanism. Electrical connec'- tions may be made to this condenser through the medium of conductors 27 and 28.

In Fig. 6 is shown an alternative structure which is an improvement over that of Fig. 4. The variable plate 29 is substantially the same as plate 15 in Fig. 4, except that the arrangement for attaching to the casing is somewhat altered as a matter of convenience. Instead of the small knob 17 ,as in the structure of Fig. 4,' there is provided a shoe 30 of insulating material, which is yieldably attached to the member 31 by means of the pins 32, whichslide in apertures provided in the shoe 30. A pair of helical springs 33 function to press the shoe 30 radially against the variable plate 29. The member 31 is rigidly secured to the rotatable shaft 34.

Athe fact that the shoe 30 su tends a considerable arc and acts on the variable plate 29 at all points between its extremities. It will be readily appreciated that when the structure of Fig. 4 with the shaft 16 is rotated to`increase the capacity, there is some possibility that the variable plate 15 will spring u at points between that at which the varia le plate is fixed and the point of contact between knob 17 and the variable plate, which would result in some loss of capacity. The arrangement of Fig. 6 entirely obviates this possibility inasmuch as it presses on the variable plate over an arc which is almost equal to the entire arc of the variable plate.

Many possible modifications of this invention will be readily apparent to those skilled in the art, and it is accordin ly not to be construed as limited except y the scope of the appended claims.

I claim:

1. A variable electrostatic condenser comprising a fixed plate having a curvilinear surface, a springy flexible plate electrically separated from said first-mentioned plate and having the form of a spiral, and a rotatable vshaft to which said flexible plate is connected, said shaft being operable to efaeeaiee lect a picking1 up and laying down open ation of said Hexible plate with respect to said xed plate.

2. A variable electrostatic condense? compising a plate having the form of an annulns, a curved springy flexible plate electiically separated 'from said first-mentioned plate, one end of said flexible plate being insnlatively attached to said first-mentioned plate, and means 'for vaiably flexing said iiexible plate toward and away ioni said iii'sbmentioned plate 'for varying the electrostatic capacity between said plates.

3. A. variable electrostatic condenser' com` pricing a plate having the orin of an annnlns, a :dexible late disposed Within said annulus, said flexible plate having the form of a spiral, one end of which is insulativel'y secured to sai-d annulus, a rotatable shaft substantially concentric with said annnlus, the inner end of said idexible plate being connected to said shaft, said shaft being operable upon notation in one direction to eiecta movement o the exterior surface of said exible plate toward the inteior son lace of said liiist-Inentioned plate and vice Versa.

et. A variable condenser comprising a nxed cnxviform metallic condnctoi` sheet, an insulating sheet thereon, a flexible springy metallic conductor sheet, and means com rising a rotatable knob toi flexing seid exible condnctoi1 sheet to vaiy the capacity of the condenser,

5, lin a Variable electrostatic condensei, an annule? plete member, an expansihle and contractible capacity varying element disposed Within said annular plate member9 and means operable for controlling said last mentioned element so that yit may possess a larger or smaller compass for ellecting capacity variations between said elements.

6. ln a device of the class described, the

combination oi' a conductor element el cifcnlai imno, an' adjustable condnctoi element of spiral form, one being contained Within the other, and means for contracting or expanding,I the conductor element of spinal 'forni 'to bring less on more of its sulface adiacent to the othe' element.

7. lin a device of the class described, the combination of a conductor element of circnlar 'tot-m, an adjg'nstalole conductor element curved to correspond in shape with the first named element, the said adjustable element being encompassed by the rst named element, and n'ieans for controlling the adjustable element so that more oi* less of its snrlace ma move towards or 'trom the rst named e ement. f

ln testimony Wlieieof l ax my signature. WlLSUN AULL, Jn. 

